1. Field of the Invention
The present invention relates to a method of controlling recording in a hard disk drive (HDD), and more particularly, to a method of compensating for an error in a recording start position to prevent a head gap and an HDD using the same.
2. Description of Related Art
A hard disk drive (HDD) includes a plurality of magnetic heads combined with rotating disks. A head writes and reads data by magnetizing a disk surface and sensing a magnetic field. The magnetic head having a write component for magnetizing a disk and a separate read component for sensing a magnetic field of the disk has been developed. The read component is typically made of a magneto-resistive (MR) material. The resistance of the MR material changes according to a magnetic field of a disk. A head having an MR read component is generally called an MR head.
The head is generally attached to a curved arm combined with a sub-assembly called a head gimbal assembly (HGA). The HGA is combined with an actuator arm. The actuator arm includes a voice coil motor (VCM) for moving the head across a disk surface.
Information is typically stored in concentric tracks formed across each disk surface. Each track is typically divided into segments. The VCM and the actuator arm move the head from one track of the disk to another.
It is preferable that the head be maintained on the center of each track to exactly write and read data. Servo sectors include servo bursts located opposite to each other on the centerline of the track to control a position of the head. Signals generated due to the servo bursts cause a position error signal (PES) that affects a position of the head on the centerline of each track.
FIG. 1 illustrates a format of data recorded on tracks of an HDD. Referring to FIG. 1, each track includes a servo sector 102 and a data sector 104. Servo sectors 102 exist on straight lines in the radius direction of a disk and are apart from each other by equal angles in the circumference direction of the disk. One or more data sectors 104 exist between adjacent servo sectors 102. Each data sector 104 contains a fixed number of bits, and a servo sector 102 may be placed by dividing a data sector 104.
A predetermined distance (a guide gap) 106 exists between a servo sector 102 and a data sector 104 and between data sectors 104. The guide gap 106 prevents servo sectors 102 and data sectors 104 from being erased by a write head and is set by considering a distance between the write head and a read head and a minimum linear velocity on the disk.
The beginning of a servo sector 102 is detected using a servo address mark recorded in the servo sector 102. A data sector pulse is used to notify the beginning of a data sector 104. As illustrated in FIG. 1, the data sector pulse is generated by a read/write channel circuit (generally a channel chip), at every fixed time interval based on the servo address mark, i.e., at every interval comprising a data sector 104 from a position delayed by the guide gap 106 from the ending of a servo sector 102. The data sector pulse timing for generating the data sector pulse is different according to zones and is registered in a zone map table.
Thus, the HDD performs an operation of writing or reading data to or from a data sector 104 based on the data sector pulse.
In the HDD, MR heads including an inductive write head and a read head made of an MR material are used. The write head and the read head are apart from each other by a predetermined gap in the disk track direction and also may have an offset in the disk radius direction.
FIGS. 2A and 2B illustrate different magnetic recording heads. In a magnetic recording head illustrated in FIG. 2A, a write head and a read head are apart from each other by a gap L in the disk track direction and have an offset in the disk radius direction. In a magnetic recording head illustrated in FIG. 2B, a write head and a read head are apart from each other by the gap L in the disk track direction.
In the HDD, a disk is rotated with a constant angular velocity, e.g., 7,200 rpm, by a spindle motor. Accordingly, a linear velocity varies according to a position on the disk.
Thus, influences by the gap between the write head and the read head vary according to a position on the disk. That is, since the linear velocity is faster in the outer circumference of the disk than in the inner circumference, a head gap time is shorter in the outer circumference of the disk than in the inner circumference. Here, the head gap time is the time required to move the head by the head gap.
FIG. 3 schematically illustrates influences of a head gap and a linear velocity in a write operation of an HDD. Referring to FIG. 3, the linear velocity is faster in the outer circumference of a disk than in the inner circumference, and therefore, a head gap time is shorter in the outer circumference of the disk than the inner circumference (T_od<T_id).
Conventionally, in considering the head gap, the servo sector and the data sector, the data sectors are arranged being apart from each other by a gap corresponding the head gap timing that is, a distance considering the minimum linear velocity (a guide gap).
However, the guide gap decreases the usage efficiency of a data area and increases the length of a data preamble because an unnecessary write operation is performed between a servo sector and a data sector.
FIGS. 4(A) through 4(K) are waveform diagrams for illustrating a conventional method of controlling recording in an HDD. FIG. 4A illustrates a servo gate signal for representing a servo sector zone. FIG. 4B illustrates a head gap time (Td_WR_od), FIG. 4C illustrates a data sector pulse, FIG. 4D illustrates write gate timing, FIG. 4E illustrates a data recording area, and FIG. 4F illustrates read gate timing, in the outer circumference. FIG. 4G illustrates a head gap time (Td_WR_id), FIG. 4H illustrates a data sector pulse, FIG. 4I illustrates write gate timing, FIG. 4J illustrates a data recording area, and FIG. 4K illustrates read gate timing, in the inner circumference.
Referring to FIGS. 4(A) through 4(K), the data sector pulse is generated after a fixed time interval from the servo gate signal in the inner and outer circumferences, and a read operation and a write operation are performed by synchronizing with the data sector pulse.
To prevent a servo sector from being erased by the write operation performed in synchronization with the data sector pulse, the data sector pulse should be generated after a time interval of a from the servo gate signal. Accordingly, a gap corresponding to the time interval of a, i.e., a guide gap, must exist between a servo sector and a data sector and between data sectors.
As illustrated in FIGS. 4E and 4J, the write operation is unnecessarily performed between a servo sector and a data sector. In other words, an unnecessary write operation is performed in a guide gap. In the write operation, a data preamble is recorded until a data sector address mark is detected. Thus, according to the conventional method illustrated in FIG. 4, data preambles are unnecessarily recorded in data gaps.
Techniques for beginning a write operation from the start portion of a data sector by measuring a head gap time and using the measured time are disclosed in Korean patent publication No. 2004-86132 and Japanese patent publication Nos. 1994-176486, 1995-326032, and 2003-151101. However, since the head gap time is measured and compensated for (Japan patent publication Nos. 1994-176486 and 2003-151101 and Korea patent publication No. 2004-86132) or an offset and a skew angle are measured and compensated for (Japan patent publication No. 1995-326032) by recording a predetermined compensation pattern on a disk and reading this pattern through a read head, an extra head gap time measurement device is required or a processing time is longer.
In addition, since a guide gap considering a minimum linear velocity is set as described in FIG. 4, the data usage efficiency is low.